1. Field of the Invention
This invention relates to a method and apparatus for the vitrification of and reduction in volume of fine particulate materials, e.g., incinerator ash, and more particularly to vitrification and volume reduction of fine particulate materials in which the source of heat is a plasma arc torch and to products produced by such method.
2. Description of the Related Art
A large percentage, perhaps as much as fifty percent (50%), of the waste material generated throughout this country and the world is in the form of fine particulate. "Fine particulate" is intended to include by way of example such materials as sawdust, mineral powder, material shavings, dirt, dust and ash and generally refers to substantially non-metallic material with particle sizes up to 1 mm in its maximum dimension. A refractory, heat insulative ash product often comes from an incineration process performed to reduce the volume of larger volume waste items. By its nature, most fine particle material tends to have very low density and is subject to being disturbed by air flow or wind and, if disturbed, may be blown into the surrounding atmosphere. In addition, because there is so much volume of this fine waste, a large amount of space is required for disposal.
In certain instances, as for example in fine incinerator ash materials, a component of the fine particulate comprises oxides of some heavy metals. When unconfined, these heavy metal oxides, i.e., oxides of lead, iron, chromium, cadmium, arsenic, and mercury, tend to leach out of the ash or powder and contaminate the ground or water supply. Also to be noted is that such heavy metal components when subjected to high temperature, as in the method of the invention will vaporize.
In the prior art incineration furnaces, the typical refractory wall material will require replacement or repair after approximately three years of service.
There has been an increased public awareness of the need to reduce the volume of waste, both to save on the amount of space allocated to landfill operations and to avoid contamination of surrounding areas. Landfill sites are being filled up at a rapid rate, and it has become increasingly difficult to locate satisfactory new sites because of negative public sentiment.
The basic method and apparatus employed in practicing the invention disclosed below depends on a high-temperature low mass, high enthalpy heat source such as is taught in U.S. Pat. No. 3,779,182 to the present inventor for a REFUSE CONVERTING METHOD AND APPARATUS UTILIZING LONG ARC COLUMN FORMING PLASMA TORCHES, the teaching of which patent is incorporated herein by reference. Certain modifications and improvements to the apparatus of the '182 patent are disclosed below. The gas fed plasma torch used in the prior '182 patent and in the present invention has the useful properties of achieving very high temperatures and of requiring a relatively very small amount of gas in the heat-delivery process. According to the method disclosed below, both these properties are essential to the principles of the invention.
It is therefore an object of this invention to provide a process directed to the significant reduction of volume of fine particulate waste.
It is an additional object of the invention to process the resultant densified material into a useful form for recycling.
Other objects and advantages will be more fully apparent from the following disclosure and appended claims.